This invention relates to a lock of the type having a latch bolt and a positioning rod which can easily be changed in its direction in a lock, especially one with a latch bolt and a dead bolt. The latch bolt can automatically extend out of the faceplate when the door is closed and the dead bolt can be extended out by turning a button at the inside of the door or by a key at the outside of the door. As the latch bolt is shaped inclined as a triangular cone, it has a direction limitation when it is to be fixed on a door. Then makers have to produce two different kinds of locks with the latch bolt having a right or a left direction, which gives rise to inconvenience for makers, retailers and users.